Mapping Models to Code

We will skip most of this chapter –It deals with how to go from UML class diagrams to actual code –You should already have a pretty good idea how to do this Would be trickier if using a language that doesn’t support OOP for example Overview –Mappings are transformations that aim at improving one aspect of the model while preserving functionality. Activities: Optimization Realizing associations Contracts to exceptions Class models to storage schema

Transformations Source code space Forward engineering Refactoring Reverse engineering Model space Model transformation

Model Transformation Example Object design model before transformation Object design model after transformation: Advertiser + Address Player + Address LeagueOwner + Address PlayerAdvertiserLeagueOwner User + Address

Refactoring Example: Pull Up Field public class Player { private String ; //... } public class LeagueOwner { private String ; //... } public class Advertiser { private String _address; //... } public class User { private String ; } public class Player extends User { //... } public class LeagueOwner extends User { //... } public class Advertiser extends User { //... }

Refactoring Example: Pull Up Constructor Body public class User { private String ; } public class Player extends User { public Player(String ) { this. = ; } public class LeagueOwner extends User{ public LeagueOwner(String ) { this. = ; } public class Advertiser extendsUser{ public Advertiser(String ) { this. = ; } public class User { public User(String ) { this. = ; } public class Player extends User { public Player(String ) { super( ); } public class LeagueOwner extends User { public LeagueOwner(String ) { super( ); } public class Advertiser extends User { public Advertiser(String ) { super( ); }

Forward Engineering Example public class User { private String ; public String get () { return ; } public void set (String value){ = value; } public void notify(String msg) { //.... } /* Other methods omitted */ } public class LeagueOwner extends User { private int maxNumLeagues; public int getMaxNumLeagues() { return maxNumLeagues; } public void setMaxNumLeagues (int value) { maxNumLeagues = value; } /* Other methods omitted */ } User LeagueOwner +maxNumLeagues:int Object design model before transformation Source code after transformation + String +notify(msg:String)

Transformation Principles Each transformation must address a single criteria –Transformation should focus on a single design goal and not try to optimize multiple criteria (can lead to errors) Each transformation must be local –A transformation should change only a few methods or classes at once –If an interface changes then the client classes should be changed now too (keep older method around for background compatibility testing) –If you are changing many subsystems at once you are performing an architectural change

Transformation Principles Each transformation must be applied in isolation to other changes –To localize changes transformations should be applied one at a time –E.g. if improving performance of a method, don’t add new functionality at the same time Each transformation must be followed by a validation step –Validate the changes for errors –Update appropriate UML diagrams –Write new test cases to exercise new source code